This invention relates to hydraulic systems and more specifically to a hydraulic system for raising and lowering the keel of a sailboat that can be used for racing.
Most sailboats have a weighted centerboard, i.e., a keel, to provide the boat with needed stability and to resist lateral movement leeward. Since a keel tends to be relatively large in size, provision should be made to retract it, normally into a well located in the underneath side of the hull when the boat is sailing in shoal waters or with the wind. When the keel is in its raised position, the sailboat will move much faster through the water than when the keel was lowered because of the higher center of gravity and lesser water resistance when the keel is raised. However, when sailing on the wind, for example, the keel must be lowered to reduce the boat's natural tendency to drift.
During a race, it is essential to be able to raise and lower the keel as quickly as possible. Even a delay of several seconds during offensive or defensive maneuvers in close quarters or during a change in course can prevent the boat from attaining an advantageous wind position and affect the outcome of a race. However, in a racing sailboat these operations, according to the rules, must be accomplished without power which in the past has proved to be strenuous and time consuming, especially when considering how often the keel must be raised and lowered during a race. Accordingly, it is advantageous to reduce the amount of work required to raise and lower the keel, providing the speed of raising and lowering is not sacrificed and the rules are not broken.
Furthermore, the keel should be able to retract or move upward if it should strike a submerged rock, underwater surface or other obstruction so that the boat is not damaged due to the keel resisting movement toward the hull. However, this movement must be cushioned to prevent the keel from smashing into the hull, especially if the boat should capsize. The tendency of the keel to slam back toward its lowered position after disengaging such an obstruction or turning upright should also be prevented.